Many types of fans, rotors, and impellers are known. One common type of fan is the squirrel cage blower which is commonly used to move air through conduits. Another common device for moving fluid is the common axial blade fan which has radially extending propeller blades. An example of this latter device is the common room fan for moving air within a room.
The use of rotors having fins or blades of various configurations and designs is known. Typically, these machines have either open blades for moving air parallel to the axis of rotation of the fan, or have enclosed passageways of square or rectangular cross section. Typically, a fan having enclosed passageways will move air in a direction perpendicular to the axis of rotation of the fan after drawing air towards the rotor in a direction parallel to the axis of rotation. Rectangular passageways have a higher ratio of surface area to volume than do circular passageways. For this reason, the rectangular passageway design necessitates a fan having a higher weight than a fan having passageways of circular cross section construction of the same material and capable of moving the same volume of air.
Additional disadvantages of the fans known in the prior art include the use of metallic materials for constructing the fan. Metal fans lead to the possibility of sparks being generated by the fan, which is a severe safety hazard in dusty environments. Also, some metals are not resistant to certain corrosive chemicals such as acids which may be present in the air being moved by the fan. Additionally, metals often have a higher density than other materials and therefore may produce a heavier fan of a given dimension. The fabrication of metal fans typically produces sharp edges and burrs which are dangerous to handle and frequently catch dust and lint from the environment reducing the efficiency of the rotor.
The fabrication methods commonly used to manufacture fans and rotors often produce a product having significant disadvantages. Often, fans are produced from thin metal stock through a stamping process, or a heavier fan is produced by casting the fan components. Some fans are constructed of multiple components which must be satisfactorily connected. Frequently employed connectors include welding, glueing, and forming tabs in one piece of the rotor which are inserted through slots in another piece of the rotor and then bent to prevent removal. The development of economical and satisfactory connection techniques is a significant problem in the art, because the finished fan must be lightweight yet strong enough to withstand the forces exerted upon it during high speed rotation.
Typical solutions to the problems encountered in moving large volumes of air have included the use of larger fans or rotors, turning the presently existing fans at higher speeds and attempting to produce more efficient fans. The first two solutions are expensive and potentially dangerous, as large or fast moving fans have a greater chance of deforming or breaking apart. Therefore, there is a need for an efficient fan capable of moving a sufficient volume of air while being of managable size, and operating at a safe speed.